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<tr class="t-nv-h2"><td colspan="5"> Containers</td></tr>
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<tr class="t-nv"><td colspan="5"> <a href="span.html" title="cpp/header/span"><tt>&lt;span&gt;</tt></a> <span class="t-mark-rev t-since-cxx20">(C++20)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="array.html" title="cpp/header/array"><tt>&lt;array&gt;</tt></a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="vector.html" title="cpp/header/vector"><tt>&lt;vector&gt;</tt></a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="deque.html" title="cpp/header/deque"><tt>&lt;deque&gt;</tt></a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="forward_list.html" title="cpp/header/forward list"><tt>&lt;forward_list&gt;</tt></a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="list.html" title="cpp/header/list"><tt>&lt;list&gt;</tt></a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="map.html" title="cpp/header/map"><tt>&lt;map&gt;</tt></a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="set.html" title="cpp/header/set"><tt>&lt;set&gt;</tt></a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="queue.html" title="cpp/header/queue"><tt>&lt;queue&gt;</tt></a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="unordered_map.html" title="cpp/header/unordered map"><tt>&lt;unordered_map&gt;</tt></a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="unordered_set.html" title="cpp/header/unordered set"><tt>&lt;unordered_set&gt;</tt></a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="stack.html" title="cpp/header/stack"><tt>&lt;stack&gt;</tt></a></td></tr>
</table></div></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Iterators</td></tr>
<tr class="t-nv"><td colspan="5"> <a href="iterator.html" title="cpp/header/iterator"><tt>&lt;iterator&gt;</tt></a></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Ranges</td></tr>
<tr class="t-nv"><td colspan="5"> <a href="ranges.html" title="cpp/header/ranges"><tt>&lt;ranges&gt;</tt></a> <span class="t-mark-rev t-since-cxx20">(C++20)</span></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Algorithms</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="algorithm.html" title="cpp/header/algorithm"><tt>&lt;algorithm&gt;</tt></a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="execution.html" title="cpp/header/execution"><tt>&lt;execution&gt;</tt></a> <span class="t-mark-rev t-since-cxx17">(C++17)</span></td></tr>
</table></div></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Numerics</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="complex.html" title="cpp/header/complex"><tt>&lt;complex&gt;</tt></a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="random.html" title="cpp/header/random"><tt>&lt;random&gt;</tt></a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="valarray.html" title="cpp/header/valarray"><tt>&lt;valarray&gt;</tt></a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="numeric.html" title="cpp/header/numeric"><tt>&lt;numeric&gt;</tt></a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="bit.html" title="cpp/header/bit"><tt>&lt;bit&gt;</tt></a> <span class="t-mark-rev t-since-cxx20">(C++20)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="numbers.html" title="cpp/header/numbers"><tt>&lt;numbers&gt;</tt></a> <span class="t-mark-rev t-since-cxx20">(C++20)</span></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="cfenv.html" title="cpp/header/cfenv"><tt>&lt;cfenv&gt;</tt></a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="cmath.html" title="cpp/header/cmath"><tt>&lt;cmath&gt;</tt></a></td></tr>
</table></div></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Input/Output</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="iosfwd.html" title="cpp/header/iosfwd"><tt>&lt;iosfwd&gt;</tt></a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="ios.html" title="cpp/header/ios"><tt>&lt;ios&gt;</tt></a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="iomanip.html" title="cpp/header/iomanip"><tt>&lt;iomanip&gt;</tt></a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="streambuf.html" title="cpp/header/streambuf"><tt>&lt;streambuf&gt;</tt></a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="istream.html" title="cpp/header/istream"><tt>&lt;istream&gt;</tt></a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="ostream.html" title="cpp/header/ostream"><tt>&lt;ostream&gt;</tt></a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="iostream.html" title="cpp/header/iostream"><tt>&lt;iostream&gt;</tt></a></td></tr>
<tr class="t-nv"><td colspan="5"> <br>
</td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="syncstream.html" title="cpp/header/syncstream"><tt>&lt;syncstream&gt;</tt></a> <span class="t-mark-rev t-since-cxx20">(C++20)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="spanstream.html" title="cpp/header/spanstream"><tt>&lt;spanstream&gt;</tt></a> <span class="t-mark-rev t-since-cxx23">(C++23)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="sstream.html" title="cpp/header/sstream"><tt>&lt;sstream&gt;</tt></a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="fstream.html" title="cpp/header/fstream"><tt>&lt;fstream&gt;</tt></a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="cstdio.html" title="cpp/header/cstdio"><tt>&lt;cstdio&gt;</tt></a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="cinttypes.html" title="cpp/header/cinttypes"><tt>&lt;cinttypes&gt;</tt></a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="strstream.html" title="cpp/header/strstream"><tt>&lt;strstream&gt;</tt></a> <span class="t-mark">(C++98/)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <br>
</td></tr>
</table></div></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Regular expressions</td></tr>
<tr class="t-nv"><td colspan="5"> <a href="regex.html" title="cpp/header/regex"><tt>&lt;regex&gt;</tt></a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Filesystem support</td></tr>
<tr class="t-nv"><td colspan="5"> <a href="filesystem.html" title="cpp/header/filesystem"><tt>&lt;filesystem&gt;</tt></a> <span class="t-mark-rev t-since-cxx17">(C++17)</span></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Thread support</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="thread.html" title="cpp/header/thread"><tt>&lt;thread&gt;</tt></a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="atomic.html" title="cpp/header/atomic"><tt>&lt;atomic&gt;</tt></a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="mutex.html" title="cpp/header/mutex"><tt>&lt;mutex&gt;</tt></a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="shared_mutex.html" title="cpp/header/shared mutex"><tt>&lt;shared_mutex&gt;</tt></a> <span class="t-mark-rev t-since-cxx14">(C++14)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="condition_variable.html" title="cpp/header/condition variable"><tt>&lt;condition_variable&gt;</tt></a> <span class="t-mark-rev t-since-cxx11">(C++11)</span>  </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="future.html" title="cpp/header/future"><tt>&lt;future&gt;</tt></a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="stop_token.html" title="cpp/header/stop token"><tt>&lt;stop_token&gt;</tt></a> <span class="t-mark-rev t-since-cxx20">(C++20)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="semaphore.html" title="cpp/header/semaphore"><tt>&lt;semaphore&gt;</tt></a> <span class="t-mark-rev t-since-cxx20">(C++20)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <br>
</td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="latch.html" title="cpp/header/latch"><tt>&lt;latch&gt;</tt></a> <span class="t-mark-rev t-since-cxx20">(C++20)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="barrier.html" title="cpp/header/barrier"><tt>&lt;barrier&gt;</tt></a> <span class="t-mark-rev t-since-cxx20">(C++20)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <br>
</td></tr>
</table></div></td></tr>
<tr class="t-nv-h2"><td colspan="5"> C compatibility</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="cstdbool.html" title="cpp/header/cstdbool"><tt>&lt;cstdbool&gt;</tt></a> <span class="t-mark">(C++11/17/20)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="ccomplex.html" title="cpp/header/ccomplex"><tt>&lt;ccomplex&gt;</tt></a> <span class="t-mark">(C++11/17/20)</span></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="ctgmath.html" title="cpp/header/ctgmath"><tt>&lt;ctgmath&gt;</tt></a> <span class="t-mark">(C++11/17/20)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="cstdalign.html" title="cpp/header/cstdalign"><tt>&lt;cstdalign&gt;</tt></a> <span class="t-mark">(C++11/17/20)</span></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="ciso646.html" title="cpp/header/ciso646"><tt>&lt;ciso646&gt;</tt></a> <span class="t-mark-rev t-until-cxx20">(until C++20)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="stdatomic.h.html" title="cpp/header/stdatomic.h"><tt>&lt;stdatomic.h&gt;</tt></a></td></tr>
</table></div></td></tr>
</table></div><div></div></div></div></div><div class="t-navbar-sep"> </div></div>
<p>This header is part of the <a href="../utility.html" title="cpp/utility">language support</a> library.
</p>
<table class="t-dsc-begin">

<tr>
<td colspan="2"> <h3> <span class="mw-headline" id="Concepts"> Concepts</span></h3>
</td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="../utility/compare/three_way_comparable.html" title="cpp/utility/compare/three way comparable"> <span class="t-lines"><span>three_way_comparable</span><span>three_way_comparable_with</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div>
</td>
<td>  specifies that operator <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy1">&lt;=&gt;</span></span></span> produces consistent result on given types  <br> <span class="t-mark">(concept)</span> </td></tr>

<tr>
<td colspan="2"> <h3> <span class="mw-headline" id="Classes"> Classes</span></h3>
</td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="../utility/compare/partial_ordering.html" title="cpp/utility/compare/partial ordering"> <span class="t-lines"><span>partial_ordering</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div>
</td>
<td>   the result type of 3-way comparison that supports all 6 operators, is not substitutable, and allows incomparable values  <br> <span class="t-mark">(class)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="../utility/compare/weak_ordering.html" title="cpp/utility/compare/weak ordering"> <span class="t-lines"><span>weak_ordering</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div>
</td>
<td>   the result type of 3-way comparison that supports all 6 operators and is not substitutable  <br> <span class="t-mark">(class)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="../utility/compare/strong_ordering.html" title="cpp/utility/compare/strong ordering"> <span class="t-lines"><span>strong_ordering</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div>
</td>
<td>   the result type of 3-way comparison that supports all 6 operators and is substitutable   <br> <span class="t-mark">(class)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="../utility/compare/common_comparison_category.html" title="cpp/utility/compare/common comparison category"> <span class="t-lines"><span>common_comparison_category</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div>
</td>
<td>  the strongest comparison category to which all of the given types can be converted  <br> <span class="t-mark">(class template)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="../utility/compare/compare_three_way_result.html" title="cpp/utility/compare/compare three way result"> <span class="t-lines"><span>compare_three_way_result</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div>
</td>
<td>   obtains the result type of the three-way comparison operator <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy1">&lt;=&gt;</span></span></span> on given types  <br> <span class="t-mark">(class template)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="../utility/compare/compare_three_way.html" title="cpp/utility/compare/compare three way"> <span class="t-lines"><span>compare_three_way</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div>
</td>
<td>   function object implementing <span class="t-c"><span class="mw-geshi cpp source-cpp">x <span class="sy1">&lt;=&gt;</span> y</span></span>  <br> <span class="t-mark">(class)</span> </td></tr>

<tr>
<td colspan="2"> <h3> <span class="mw-headline" id="Customization_point_objects"> Customization point objects</span></h3>
</td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="../utility/compare/strong_order.html" title="cpp/utility/compare/strong order"> <span class="t-lines"><span>strong_order</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div>
</td>
<td>   performs 3-way comparison and produces a result of type <code>std::strong_ordering</code>  <br> <span class="t-mark">(customization point object)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="../utility/compare/weak_order.html" title="cpp/utility/compare/weak order"> <span class="t-lines"><span>weak_order</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div>
</td>
<td>   performs 3-way comparison and produces a result of type <code>std::weak_ordering</code>  <br> <span class="t-mark">(customization point object)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="../utility/compare/partial_order.html" title="cpp/utility/compare/partial order"> <span class="t-lines"><span>partial_order</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div>
</td>
<td>   performs 3-way comparison and produces a result of type <code>std::partial_ordering</code>  <br> <span class="t-mark">(customization point object)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="../utility/compare/compare_strong_order_fallback.html" title="cpp/utility/compare/compare strong order fallback"> <span class="t-lines"><span>compare_strong_order_fallback</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div>
</td>
<td>   performs 3-way comparison and produces a result of type <code>std::strong_ordering</code>, even if <span class="t-c"><span class="mw-geshi cpp source-cpp">operator<span class="sy1">&lt;=&gt;</span></span></span> is unavailable  <br> <span class="t-mark">(customization point object)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="../utility/compare/compare_weak_order_fallback.html" title="cpp/utility/compare/compare weak order fallback"> <span class="t-lines"><span>compare_weak_order_fallback</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div>
</td>
<td>   performs 3-way comparison and produces a result of type <code>std::weak_ordering</code>, even if <span class="t-c"><span class="mw-geshi cpp source-cpp">operator<span class="sy1">&lt;=&gt;</span></span></span> is unavailable  <br> <span class="t-mark">(customization point object)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="../utility/compare/compare_partial_order_fallback.html" title="cpp/utility/compare/compare partial order fallback"> <span class="t-lines"><span>compare_partial_order_fallback</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div>
</td>
<td>   performs 3-way comparison and produces a result of type <code>std::partial_ordering</code>, even if <span class="t-c"><span class="mw-geshi cpp source-cpp">operator<span class="sy1">&lt;=&gt;</span></span></span> is unavailable  <br> <span class="t-mark">(customization point object)</span> </td></tr>

<tr>
<td colspan="2"> <h3> <span class="mw-headline" id="Functions"> Functions</span></h3>
</td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="../utility/compare/named_comparison_functions.html" title="cpp/utility/compare/named comparison functions"> <span class="t-lines"><span>is_eq</span><span>is_neq</span><span>is_lt</span><span>is_lteq</span><span>is_gt</span><span>is_gteq</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div>
</td>
<td>   named comparison functions  <br> <span class="t-mark">(function)</span> </td></tr>
</table>
<h3><span class="mw-headline" id="Synopsis">Synopsis</span></h3>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">namespace</span> std <span class="br0">{</span>
  <span class="co1">// comparison category types</span>
  <span class="kw1">class</span> partial_ordering<span class="sy4">;</span>
  <span class="kw1">class</span> weak_ordering<span class="sy4">;</span>
  <span class="kw1">class</span> strong_ordering<span class="sy4">;</span>
 
  <span class="co1">// named comparison functions</span>
  <span class="kw4">constexpr</span> <span class="kw4">bool</span> is_eq  <span class="br0">(</span>partial_ordering cmp<span class="br0">)</span> <span class="kw1">noexcept</span> <span class="br0">{</span> <span class="kw1">return</span> cmp <span class="sy1">==</span> <span class="nu0">0</span><span class="sy4">;</span> <span class="br0">}</span>
  <span class="kw4">constexpr</span> <span class="kw4">bool</span> is_neq <span class="br0">(</span>partial_ordering cmp<span class="br0">)</span> <span class="kw1">noexcept</span> <span class="br0">{</span> <span class="kw1">return</span> cmp <span class="sy3">!</span><span class="sy1">=</span> <span class="nu0">0</span><span class="sy4">;</span> <span class="br0">}</span>
  <span class="kw4">constexpr</span> <span class="kw4">bool</span> is_lt  <span class="br0">(</span>partial_ordering cmp<span class="br0">)</span> <span class="kw1">noexcept</span> <span class="br0">{</span> <span class="kw1">return</span> cmp <span class="sy1">&lt;</span> <span class="nu0">0</span><span class="sy4">;</span> <span class="br0">}</span>
  <span class="kw4">constexpr</span> <span class="kw4">bool</span> is_lteq<span class="br0">(</span>partial_ordering cmp<span class="br0">)</span> <span class="kw1">noexcept</span> <span class="br0">{</span> <span class="kw1">return</span> cmp <span class="sy1">&lt;=</span> <span class="nu0">0</span><span class="sy4">;</span> <span class="br0">}</span>
  <span class="kw4">constexpr</span> <span class="kw4">bool</span> is_gt  <span class="br0">(</span>partial_ordering cmp<span class="br0">)</span> <span class="kw1">noexcept</span> <span class="br0">{</span> <span class="kw1">return</span> cmp <span class="sy1">&gt;</span> <span class="nu0">0</span><span class="sy4">;</span> <span class="br0">}</span>
  <span class="kw4">constexpr</span> <span class="kw4">bool</span> is_gteq<span class="br0">(</span>partial_ordering cmp<span class="br0">)</span> <span class="kw1">noexcept</span> <span class="br0">{</span> <span class="kw1">return</span> cmp <span class="sy1">&gt;=</span> <span class="nu0">0</span><span class="sy4">;</span> <span class="br0">}</span>
 
  <span class="co1">// common comparison category type</span>
  <span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span>... <span class="me1">Ts</span><span class="sy1">&gt;</span>
  <span class="kw1">struct</span> common_comparison_category <span class="br0">{</span>
    <span class="kw1">using</span> type <span class="sy1">=</span> <span class="coMULTI">/* see description */</span><span class="sy4">;</span>
  <span class="br0">}</span><span class="sy4">;</span>
  <span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span>... <span class="me1">Ts</span><span class="sy1">&gt;</span>
    <span class="kw1">using</span> common_comparison_category_t <span class="sy1">=</span> <span class="kw1">typename</span> common_comparison_category<span class="sy1">&lt;</span>Ts...<span class="sy1">&gt;</span><span class="sy4">::</span><span class="me2">type</span><span class="sy4">;</span>
 
  <span class="co1">// concept three_way_comparable</span>
  <span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span> T, <span class="kw1">class</span> Cat <span class="sy1">=</span> partial_ordering<span class="sy1">&gt;</span>
    concept three_way_comparable <span class="sy1">=</span> <span class="coMULTI">/* see description */</span><span class="sy4">;</span>
  <span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span> T, <span class="kw1">class</span> U, <span class="kw1">class</span> Cat <span class="sy1">=</span> partial_ordering<span class="sy1">&gt;</span>
    concept three_way_comparable_with <span class="sy1">=</span> <span class="coMULTI">/* see description */</span><span class="sy4">;</span>
 
  <span class="co1">// result of three-way comparison</span>
  <span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span> T, <span class="kw1">class</span> U <span class="sy1">=</span> T<span class="sy1">&gt;</span> <span class="kw1">struct</span> compare_three_way_result<span class="sy4">;</span>
 
  <span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span> T, <span class="kw1">class</span> U <span class="sy1">=</span> T<span class="sy1">&gt;</span>
    <span class="kw1">using</span> compare_three_way_result_t <span class="sy1">=</span> <span class="kw1">typename</span> compare_three_way_result<span class="sy1">&lt;</span>T, U<span class="sy1">&gt;</span><span class="sy4">::</span><span class="me2">type</span><span class="sy4">;</span>
 
  <span class="co1">// class compare_three_way</span>
  <span class="kw1">struct</span> compare_three_way<span class="sy4">;</span>
 
  <span class="co1">// comparison algorithms</span>
  <span class="kw1">inline</span> <span class="kw1">namespace</span> <span class="coMULTI">/* unspecified */</span> <span class="br0">{</span>
    <span class="kw1">inline</span> <span class="kw4">constexpr</span> <span class="coMULTI">/* unspecified */</span> strong_order <span class="sy1">=</span> <span class="coMULTI">/* unspecified */</span><span class="sy4">;</span>
    <span class="kw1">inline</span> <span class="kw4">constexpr</span> <span class="coMULTI">/* unspecified */</span> weak_order <span class="sy1">=</span> <span class="coMULTI">/* unspecified */</span><span class="sy4">;</span>
    <span class="kw1">inline</span> <span class="kw4">constexpr</span> <span class="coMULTI">/* unspecified */</span> partial_order <span class="sy1">=</span> <span class="coMULTI">/* unspecified */</span><span class="sy4">;</span>
    <span class="kw1">inline</span> <span class="kw4">constexpr</span> <span class="coMULTI">/* unspecified */</span> compare_strong_order_fallback <span class="sy1">=</span> <span class="coMULTI">/* unspecified */</span><span class="sy4">;</span>
    <span class="kw1">inline</span> <span class="kw4">constexpr</span> <span class="coMULTI">/* unspecified */</span> compare_weak_order_fallback <span class="sy1">=</span> <span class="coMULTI">/* unspecified */</span><span class="sy4">;</span>
    <span class="kw1">inline</span> <span class="kw4">constexpr</span> <span class="coMULTI">/* unspecified */</span> compare_partial_order_fallback <span class="sy1">=</span> <span class="coMULTI">/* unspecified */</span><span class="sy4">;</span>
  <span class="br0">}</span>
<span class="br0">}</span></pre></div></div>
<h4><span class="mw-headline" id="Concept_three_way_comparable">Concept <a href="../utility/compare/three_way_comparable.html" title="cpp/utility/compare/three way comparable"><code>three_way_comparable</code></a></span></h4>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">namespace</span> std <span class="br0">{</span>
  <span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span> T, <span class="kw1">class</span> Cat<span class="sy1">&gt;</span>
    concept __ComparesAs <span class="sy1">=</span>                <span class="co1">// exposition only</span>
      same_as<span class="sy1">&lt;</span>common_comparison_category_t<span class="sy1">&lt;</span>T, Cat<span class="sy1">&gt;</span>, Cat<span class="sy1">&gt;</span><span class="sy4">;</span>
 
  <span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span> T, <span class="kw1">class</span> U<span class="sy1">&gt;</span>
    concept __PartiallyOrderedWith <span class="sy1">=</span>      <span class="co1">// exposition only</span>
      requires<span class="br0">(</span><span class="kw4">const</span> remove_reference_t<span class="sy1">&lt;</span>T<span class="sy1">&gt;</span><span class="sy3">&amp;</span> t, <span class="kw4">const</span> remove_reference_t<span class="sy1">&lt;</span>U<span class="sy1">&gt;</span><span class="sy3">&amp;</span> u<span class="br0">)</span> <span class="br0">{</span>
        <span class="br0">{</span> t <span class="sy1">&lt;</span>  u <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">&gt;</span> <a href="../concepts/boolean-testable.html"><span class="kw100">boolean-testable</span></a><span class="sy4">;</span>
        <span class="br0">{</span> t <span class="sy1">&gt;</span>  u <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">&gt;</span> <a href="../concepts/boolean-testable.html"><span class="kw100">boolean-testable</span></a><span class="sy4">;</span>
        <span class="br0">{</span> t <span class="sy1">&lt;=</span> u <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">&gt;</span> <a href="../concepts/boolean-testable.html"><span class="kw100">boolean-testable</span></a><span class="sy4">;</span>
        <span class="br0">{</span> t <span class="sy1">&gt;=</span> u <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">&gt;</span> <a href="../concepts/boolean-testable.html"><span class="kw100">boolean-testable</span></a><span class="sy4">;</span>
        <span class="br0">{</span> u <span class="sy1">&lt;</span>  t <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">&gt;</span> <a href="../concepts/boolean-testable.html"><span class="kw100">boolean-testable</span></a><span class="sy4">;</span>
        <span class="br0">{</span> u <span class="sy1">&gt;</span>  t <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">&gt;</span> <a href="../concepts/boolean-testable.html"><span class="kw100">boolean-testable</span></a><span class="sy4">;</span>
        <span class="br0">{</span> u <span class="sy1">&lt;=</span> t <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">&gt;</span> <a href="../concepts/boolean-testable.html"><span class="kw100">boolean-testable</span></a><span class="sy4">;</span>
        <span class="br0">{</span> u <span class="sy1">&gt;=</span> t <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">&gt;</span> <a href="../concepts/boolean-testable.html"><span class="kw100">boolean-testable</span></a><span class="sy4">;</span>
      <span class="br0">}</span><span class="sy4">;</span>
 
  <span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span> T, <span class="kw1">class</span> Cat <span class="sy1">=</span> partial_ordering<span class="sy1">&gt;</span>
    concept three_way_comparable <span class="sy1">=</span>
      __WeaklyEqualityComparableWith<span class="sy1">&lt;</span>T, T<span class="sy1">&gt;</span> <span class="sy3">&amp;&amp;</span>
      __PartiallyOrderedWith<span class="sy1">&lt;</span>T, T<span class="sy1">&gt;</span> <span class="sy3">&amp;&amp;</span>
      requires<span class="br0">(</span><span class="kw4">const</span> remove_reference_t<span class="sy1">&lt;</span>T<span class="sy1">&gt;</span><span class="sy3">&amp;</span> a, <span class="kw4">const</span> remove_reference_t<span class="sy1">&lt;</span>T<span class="sy1">&gt;</span><span class="sy3">&amp;</span> b<span class="br0">)</span> <span class="br0">{</span>
        <span class="br0">{</span> a <span class="sy1">&lt;=&gt;</span> b <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">&gt;</span> __ComparesAs<span class="sy1">&lt;</span>Cat<span class="sy1">&gt;</span><span class="sy4">;</span>
      <span class="br0">}</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div></div>
<h4><span class="mw-headline" id="Concept_three_way_comparable_with">Concept <a href="../utility/compare/three_way_comparable.html" title="cpp/utility/compare/three way comparable"><code>three_way_comparable_with</code></a></span></h4>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">namespace</span> std <span class="br0">{</span>
  <span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span> T, <span class="kw1">class</span> U, <span class="kw1">class</span> Cat <span class="sy1">=</span> partial_ordering<span class="sy1">&gt;</span>
    concept three_way_comparable_with <span class="sy1">=</span>
      __WeaklyEqualityComparableWith<span class="sy1">&lt;</span>T, U<span class="sy1">&gt;</span> <span class="sy3">&amp;&amp;</span>
      __PartiallyOrderedWith<span class="sy1">&lt;</span>T, U<span class="sy1">&gt;</span> <span class="sy3">&amp;&amp;</span>
      three_way_comparable<span class="sy1">&lt;</span>T, Cat<span class="sy1">&gt;</span> <span class="sy3">&amp;&amp;</span>
      three_way_comparable<span class="sy1">&lt;</span>U, Cat<span class="sy1">&gt;</span> <span class="sy3">&amp;&amp;</span>
      common_reference_with<span class="sy1">&lt;</span><span class="kw4">const</span> remove_reference_t<span class="sy1">&lt;</span>T<span class="sy1">&gt;</span><span class="sy3">&amp;</span>, <span class="kw4">const</span> remove_reference_t<span class="sy1">&lt;</span>U<span class="sy1">&gt;</span><span class="sy3">&amp;</span><span class="sy1">&gt;</span> <span class="sy3">&amp;&amp;</span>
      three_way_comparable<span class="sy1">&lt;</span>
        common_reference_t<span class="sy1">&lt;</span>
          <span class="kw4">const</span> remove_reference_t<span class="sy1">&lt;</span>T<span class="sy1">&gt;</span><span class="sy3">&amp;</span>, <span class="kw4">const</span> remove_reference_t<span class="sy1">&lt;</span>U<span class="sy1">&gt;</span><span class="sy3">&amp;</span><span class="sy1">&gt;</span>, Cat<span class="sy1">&gt;</span> <span class="sy3">&amp;&amp;</span>
      requires<span class="br0">(</span><span class="kw4">const</span> remove_reference_t<span class="sy1">&lt;</span>T<span class="sy1">&gt;</span><span class="sy3">&amp;</span> t, <span class="kw4">const</span> remove_reference_t<span class="sy1">&lt;</span>U<span class="sy1">&gt;</span><span class="sy3">&amp;</span> u<span class="br0">)</span> <span class="br0">{</span>
        <span class="br0">{</span> t <span class="sy1">&lt;=&gt;</span> u <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">&gt;</span> __ComparesAs<span class="sy1">&lt;</span>Cat<span class="sy1">&gt;</span><span class="sy4">;</span>
        <span class="br0">{</span> u <span class="sy1">&lt;=&gt;</span> t <span class="br0">}</span> <span class="sy2">-</span><span class="sy1">&gt;</span> __ComparesAs<span class="sy1">&lt;</span>Cat<span class="sy1">&gt;</span><span class="sy4">;</span>
      <span class="br0">}</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div></div>
<h4><span class="mw-headline" id="Class_std::partial_ordering">Class <span class="t-lc">std::partial_ordering</span></span></h4>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">namespace</span> std <span class="br0">{</span>
  <span class="kw1">class</span> partial_ordering <span class="br0">{</span>
    <span class="kw4">int</span> value<span class="sy4">;</span>          <span class="co1">// exposition only</span>
    <span class="kw4">bool</span> is_ordered<span class="sy4">;</span>    <span class="co1">// exposition only</span>
 
    <span class="co1">// exposition-only constructors</span>
    <span class="kw4">constexpr</span> <span class="kw1">explicit</span>
      partial_ordering<span class="br0">(</span>eq v<span class="br0">)</span> <span class="kw1">noexcept</span> <span class="sy4">:</span>
        value<span class="br0">(</span><span class="kw4">int</span><span class="br0">(</span>v<span class="br0">)</span><span class="br0">)</span>, is_ordered<span class="br0">(</span><span class="kw2">true</span><span class="br0">)</span> <span class="br0">{</span><span class="br0">}</span>      <span class="co1">// exposition only</span>
    <span class="kw4">constexpr</span> <span class="kw1">explicit</span>
      partial_ordering<span class="br0">(</span>ord v<span class="br0">)</span> <span class="kw1">noexcept</span> <span class="sy4">:</span>
        value<span class="br0">(</span><span class="kw4">int</span><span class="br0">(</span>v<span class="br0">)</span><span class="br0">)</span>, is_ordered<span class="br0">(</span><span class="kw2">true</span><span class="br0">)</span> <span class="br0">{</span><span class="br0">}</span>     <span class="co1">// exposition only</span>
    <span class="kw4">constexpr</span> <span class="kw1">explicit</span>
      partial_ordering<span class="br0">(</span>ncmp v<span class="br0">)</span> <span class="kw1">noexcept</span> <span class="sy4">:</span>
        value<span class="br0">(</span><span class="kw4">int</span><span class="br0">(</span>v<span class="br0">)</span><span class="br0">)</span>, is_ordered<span class="br0">(</span><span class="kw2">false</span><span class="br0">)</span> <span class="br0">{</span><span class="br0">}</span>   <span class="co1">// exposition only</span>
 
  <span class="kw1">public</span><span class="sy4">:</span>
    <span class="co1">// valid values</span>
    <span class="kw4">static</span> <span class="kw4">const</span> partial_ordering less<span class="sy4">;</span>
    <span class="kw4">static</span> <span class="kw4">const</span> partial_ordering equivalent<span class="sy4">;</span>
    <span class="kw4">static</span> <span class="kw4">const</span> partial_ordering greater<span class="sy4">;</span>
    <span class="kw4">static</span> <span class="kw4">const</span> partial_ordering unordered<span class="sy4">;</span>
 
    <span class="co1">// comparisons</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">==</span><span class="br0">(</span>partial_ordering v, <span class="coMULTI">/* unspecified */</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span>
      operator<span class="sy1">==</span><span class="br0">(</span>partial_ordering v, partial_ordering w<span class="br0">)</span> <span class="kw1">noexcept</span> <span class="sy1">=</span> <span class="kw1">default</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">&lt;</span> <span class="br0">(</span>partial_ordering v, <span class="coMULTI">/* unspecified */</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">&gt;</span> <span class="br0">(</span>partial_ordering v, <span class="coMULTI">/* unspecified */</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">&lt;=</span><span class="br0">(</span>partial_ordering v, <span class="coMULTI">/* unspecified */</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">&gt;=</span><span class="br0">(</span>partial_ordering v, <span class="coMULTI">/* unspecified */</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">&lt;</span> <span class="br0">(</span><span class="coMULTI">/* unspecified */</span>, partial_ordering v<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">&gt;</span> <span class="br0">(</span><span class="coMULTI">/* unspecified */</span>, partial_ordering v<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">&lt;=</span><span class="br0">(</span><span class="coMULTI">/* unspecified */</span>, partial_ordering v<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">&gt;=</span><span class="br0">(</span><span class="coMULTI">/* unspecified */</span>, partial_ordering v<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> partial_ordering
      operator<span class="sy1">&lt;=&gt;</span><span class="br0">(</span>partial_ordering v, <span class="coMULTI">/* unspecified */</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> partial_ordering
      operator<span class="sy1">&lt;=&gt;</span><span class="br0">(</span><span class="coMULTI">/* unspecified */</span>, partial_ordering v<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
  <span class="br0">}</span><span class="sy4">;</span>
 
  <span class="co1">// valid values' definitions</span>
  <span class="kw1">inline</span> <span class="kw4">constexpr</span> partial_ordering partial_ordering<span class="sy4">::</span><span class="me2">less</span><span class="br0">(</span>ord<span class="sy4">::</span><span class="me2">less</span><span class="br0">)</span><span class="sy4">;</span>
  <span class="kw1">inline</span> <span class="kw4">constexpr</span> partial_ordering partial_ordering<span class="sy4">::</span><span class="me2">equivalent</span><span class="br0">(</span>eq<span class="sy4">::</span><span class="me2">equivalent</span><span class="br0">)</span><span class="sy4">;</span>
  <span class="kw1">inline</span> <span class="kw4">constexpr</span> partial_ordering partial_ordering<span class="sy4">::</span><span class="me2">greater</span><span class="br0">(</span>ord<span class="sy4">::</span><span class="me2">greater</span><span class="br0">)</span><span class="sy4">;</span>
  <span class="kw1">inline</span> <span class="kw4">constexpr</span> partial_ordering partial_ordering<span class="sy4">::</span><span class="me2">unordered</span><span class="br0">(</span>ncmp<span class="sy4">::</span><span class="me2">unordered</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div></div>
<h4><span class="mw-headline" id="Class_std::weak_ordering">Class <span class="t-lc">std::weak_ordering</span></span></h4>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">namespace</span> std <span class="br0">{</span>
  <span class="kw1">class</span> weak_ordering <span class="br0">{</span>
    <span class="kw4">int</span> value<span class="sy4">;</span>  <span class="co1">// exposition only</span>
 
    <span class="co1">// exposition-only constructors</span>
    <span class="kw4">constexpr</span> <span class="kw1">explicit</span> weak_ordering<span class="br0">(</span>eq v<span class="br0">)</span> <span class="kw1">noexcept</span> <span class="sy4">:</span> value<span class="br0">(</span><span class="kw4">int</span><span class="br0">(</span>v<span class="br0">)</span><span class="br0">)</span> <span class="br0">{</span><span class="br0">}</span>  <span class="co1">// exposition only</span>
    <span class="kw4">constexpr</span> <span class="kw1">explicit</span> weak_ordering<span class="br0">(</span>ord v<span class="br0">)</span> <span class="kw1">noexcept</span> <span class="sy4">:</span> value<span class="br0">(</span><span class="kw4">int</span><span class="br0">(</span>v<span class="br0">)</span><span class="br0">)</span> <span class="br0">{</span><span class="br0">}</span> <span class="co1">// exposition only</span>
 
  <span class="kw1">public</span><span class="sy4">:</span>
    <span class="co1">// valid values</span>
    <span class="kw4">static</span> <span class="kw4">const</span> weak_ordering less<span class="sy4">;</span>
    <span class="kw4">static</span> <span class="kw4">const</span> weak_ordering equivalent<span class="sy4">;</span>
    <span class="kw4">static</span> <span class="kw4">const</span> weak_ordering greater<span class="sy4">;</span>
 
    <span class="co1">// conversions</span>
    <span class="kw4">constexpr</span> operator partial_ordering<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
 
    <span class="co1">// comparisons</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">==</span><span class="br0">(</span>weak_ordering v, <span class="coMULTI">/* unspecified */</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">==</span><span class="br0">(</span>weak_ordering v, weak_ordering w<span class="br0">)</span> <span class="kw1">noexcept</span> <span class="sy1">=</span> <span class="kw1">default</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">&lt;</span> <span class="br0">(</span>weak_ordering v, <span class="coMULTI">/* unspecified */</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">&gt;</span> <span class="br0">(</span>weak_ordering v, <span class="coMULTI">/* unspecified */</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">&lt;=</span><span class="br0">(</span>weak_ordering v, <span class="coMULTI">/* unspecified */</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">&gt;=</span><span class="br0">(</span>weak_ordering v, <span class="coMULTI">/* unspecified */</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">&lt;</span> <span class="br0">(</span><span class="coMULTI">/* unspecified */</span>, weak_ordering v<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">&gt;</span> <span class="br0">(</span><span class="coMULTI">/* unspecified */</span>, weak_ordering v<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">&lt;=</span><span class="br0">(</span><span class="coMULTI">/* unspecified */</span>, weak_ordering v<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">&gt;=</span><span class="br0">(</span><span class="coMULTI">/* unspecified */</span>, weak_ordering v<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> weak_ordering
      operator<span class="sy1">&lt;=&gt;</span><span class="br0">(</span>weak_ordering v, <span class="coMULTI">/* unspecified */</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> weak_ordering
      operator<span class="sy1">&lt;=&gt;</span><span class="br0">(</span><span class="coMULTI">/* unspecified */</span>, weak_ordering v<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
  <span class="br0">}</span><span class="sy4">;</span>
 
  <span class="co1">// valid values' definitions</span>
  <span class="kw1">inline</span> <span class="kw4">constexpr</span> weak_ordering weak_ordering<span class="sy4">::</span><span class="me2">less</span><span class="br0">(</span>ord<span class="sy4">::</span><span class="me2">less</span><span class="br0">)</span><span class="sy4">;</span>
  <span class="kw1">inline</span> <span class="kw4">constexpr</span> weak_ordering weak_ordering<span class="sy4">::</span><span class="me2">equivalent</span><span class="br0">(</span>eq<span class="sy4">::</span><span class="me2">equivalent</span><span class="br0">)</span><span class="sy4">;</span>
  <span class="kw1">inline</span> <span class="kw4">constexpr</span> weak_ordering weak_ordering<span class="sy4">::</span><span class="me2">greater</span><span class="br0">(</span>ord<span class="sy4">::</span><span class="me2">greater</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div></div>
<h4><span class="mw-headline" id="Class_std::strong_ordering">Class <span class="t-lc">std::strong_ordering</span></span></h4>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">namespace</span> std <span class="br0">{</span>
  <span class="kw1">class</span> strong_ordering <span class="br0">{</span>
    <span class="kw4">int</span> value<span class="sy4">;</span>  <span class="co1">// exposition only</span>
 
    <span class="co1">// exposition-only constructors</span>
    <span class="kw4">constexpr</span> <span class="kw1">explicit</span> strong_ordering<span class="br0">(</span>eq v<span class="br0">)</span> <span class="kw1">noexcept</span> <span class="sy4">:</span>
      value<span class="br0">(</span><span class="kw4">int</span><span class="br0">(</span>v<span class="br0">)</span><span class="br0">)</span> <span class="br0">{</span><span class="br0">}</span>    <span class="co1">// exposition only</span>
    <span class="kw4">constexpr</span> <span class="kw1">explicit</span> strong_ordering<span class="br0">(</span>ord v<span class="br0">)</span> <span class="kw1">noexcept</span> <span class="sy4">:</span>
      value<span class="br0">(</span><span class="kw4">int</span><span class="br0">(</span>v<span class="br0">)</span><span class="br0">)</span> <span class="br0">{</span><span class="br0">}</span>   <span class="co1">// exposition only</span>
 
  <span class="kw1">public</span><span class="sy4">:</span>
    <span class="co1">// valid values</span>
    <span class="kw4">static</span> <span class="kw4">const</span> strong_ordering less<span class="sy4">;</span>
    <span class="kw4">static</span> <span class="kw4">const</span> strong_ordering equal<span class="sy4">;</span>
    <span class="kw4">static</span> <span class="kw4">const</span> strong_ordering equivalent<span class="sy4">;</span>
    <span class="kw4">static</span> <span class="kw4">const</span> strong_ordering greater<span class="sy4">;</span>
 
    <span class="co1">// conversions</span>
    <span class="kw4">constexpr</span> operator partial_ordering<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw4">constexpr</span> operator weak_ordering<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
 
    <span class="co1">// comparisons</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">==</span><span class="br0">(</span>strong_ordering v, <span class="coMULTI">/* unspecified */</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span>
      operator<span class="sy1">==</span><span class="br0">(</span>strong_ordering v, strong_ordering w<span class="br0">)</span> <span class="kw1">noexcept</span> <span class="sy1">=</span> <span class="kw1">default</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">&lt;</span> <span class="br0">(</span>strong_ordering v, <span class="coMULTI">/* unspecified */</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">&gt;</span> <span class="br0">(</span>strong_ordering v, <span class="coMULTI">/* unspecified */</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">&lt;=</span><span class="br0">(</span>strong_ordering v, <span class="coMULTI">/* unspecified */</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">&gt;=</span><span class="br0">(</span>strong_ordering v, <span class="coMULTI">/* unspecified */</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">&lt;</span> <span class="br0">(</span><span class="coMULTI">/* unspecified */</span>, strong_ordering v<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">&gt;</span> <span class="br0">(</span><span class="coMULTI">/* unspecified */</span>, strong_ordering v<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">&lt;=</span><span class="br0">(</span><span class="coMULTI">/* unspecified */</span>, strong_ordering v<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> operator<span class="sy1">&gt;=</span><span class="br0">(</span><span class="coMULTI">/* unspecified */</span>, strong_ordering v<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> strong_ordering
      operator<span class="sy1">&lt;=&gt;</span><span class="br0">(</span>strong_ordering v, <span class="coMULTI">/* unspecified */</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    <span class="kw1">friend</span> <span class="kw4">constexpr</span> strong_ordering
    operator<span class="sy1">&lt;=&gt;</span><span class="br0">(</span><span class="coMULTI">/* unspecified */</span>, strong_ordering v<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
  <span class="br0">}</span><span class="sy4">;</span>
 
  <span class="co1">// valid values' definitions</span>
  <span class="kw1">inline</span> <span class="kw4">constexpr</span> strong_ordering strong_ordering<span class="sy4">::</span><span class="me2">less</span><span class="br0">(</span>ord<span class="sy4">::</span><span class="me2">less</span><span class="br0">)</span><span class="sy4">;</span>
  <span class="kw1">inline</span> <span class="kw4">constexpr</span> strong_ordering strong_ordering<span class="sy4">::</span><span class="me2">equal</span><span class="br0">(</span>eq<span class="sy4">::</span><span class="me2">equal</span><span class="br0">)</span><span class="sy4">;</span>
  <span class="kw1">inline</span> <span class="kw4">constexpr</span> strong_ordering strong_ordering<span class="sy4">::</span><span class="me2">equivalent</span><span class="br0">(</span>eq<span class="sy4">::</span><span class="me2">equivalent</span><span class="br0">)</span><span class="sy4">;</span>
  <span class="kw1">inline</span> <span class="kw4">constexpr</span> strong_ordering strong_ordering<span class="sy4">::</span><span class="me2">greater</span><span class="br0">(</span>ord<span class="sy4">::</span><span class="me2">greater</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div></div>
<h4><span class="mw-headline" id="Class_std::compare_three_way">Class <span class="t-lc"><a href="../utility/compare/compare_three_way.html" title="cpp/utility/compare/compare three way">std::compare_three_way</a></span></span></h4>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">namespace</span> std <span class="br0">{</span>
  <span class="kw1">struct</span> compare_three_way <span class="br0">{</span>
    <span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span> T, <span class="kw1">class</span> U<span class="sy1">&gt;</span>
    <span class="kw4">constexpr</span> <span class="kw4">auto</span> operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span>T<span class="sy3">&amp;&amp;</span> t, U<span class="sy3">&amp;&amp;</span> u<span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span>
 
    <span class="kw1">using</span> is_transparent <span class="sy1">=</span> <span class="coMULTI">/* unspecified */</span><span class="sy4">;</span>
  <span class="br0">}</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div></div>
<h3><span class="mw-headline" id="See_also">See also</span></h3>
<table class="t-dsc-begin">

<tr class="t-dsc">
<td colspan="2">  <a href="../language/operator_comparison.html#Three-way_comparison" title="cpp/language/operator comparison"> <b>three-way comparison operator</b></a> expression <i>lhs</i> <code><b>&lt;=&gt;</b></code> <i>rhs</i> <span class="t-mark-rev t-since-cxx20">(C++20)</span>
</td></tr>

</table>

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